Add historical/calgary.md (from https://github.com/daira/zcash/blob/4cc1a6b2b68a224b46135f89c99e254ac893468a/doc/zcash/calgary.md).
Add historical/calgary.md (from https://github.com/daira/zcash/blob/4cc1a6b2b68a224b46135f89c99e254ac893468a/doc/zcash/calgary.md).

Signed-off-by: Daira Hopwood <cd7d43d5556a38ce626d53826fddc46adc597539@jacaranda.org>

zcash/zips,zcash/zips,zcash/zips,zcash/zips